/*-
 * Copyright (c) 1990, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Chris Torek.
 *
 * Portions copyright (c) 1999, 2000
 * Intel Corporation.
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 * 
 *    This product includes software developed by the University of
 *    California, Berkeley, Intel Corporation, and its contributors.
 * 
 * 4. Neither the name of University, Intel Corporation, or their respective
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS, INTEL CORPORATION AND
 * CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING,
 * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS,
 * INTEL CORPORATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

#if defined(LIBC_SCCS) && !defined(lint)
#if 0
static char sccsid[] = "@(#)ftell.c	8.2 (Berkeley) 5/4/95";
#endif
static const char rcsid[] =
		"$Id: ftell.c,v 1.1.1.1 2006/05/30 06:13:51 hhzhou Exp $";
#endif /* LIBC_SCCS and not lint */

#include <sys/types.h>
#include <stdio.h>
#include <errno.h>
#include "local.h"
#include "libc_private.h"

/*
 * standard ftell function.
 */
long
ftell(fp)
	register FILE *fp;
{
	register off_t rv;
	rv = ftello(fp);
	if ((long)rv != rv) {
		errno = EOVERFLOW;
		return (-1);
	}
	return ((long)rv);
}

/*
 * ftello: return current offset.
 */
off_t
ftello(fp)
	register FILE *fp;
{
	register fpos_t pos;

	if (fp->_seek == NULL) {
		errno = ESPIPE;			/* historic practice */
		return (-1L);
	}

	FLOCKFILE(fp);
	/*
	 * Find offset of underlying I/O object, then
	 * adjust for buffered bytes.
	 */
	if (fp->_flags & __SOFF)
		pos = fp->_offset;
	else {
		pos = (*fp->_seek)(fp->_cookie, (fpos_t)0, SEEK_CUR);
		if (pos == -1) {
			FUNLOCKFILE(fp);
			return (pos);
		}
	}
	if (fp->_flags & __SRD) {
		/*
		 * Reading.  Any unread characters (including
		 * those from ungetc) cause the position to be
		 * smaller than that in the underlying object.
		 */
		pos -= fp->_r;
		if (HASUB(fp))
			pos -= fp->_ur;
	} else if (fp->_flags & __SWR && fp->_p != NULL) {
		/*
		 * Writing.  Any buffered characters cause the
		 * position to be greater than that in the
		 * underlying object.
		 */
		pos += fp->_p - fp->_bf._base;
	}
	FUNLOCKFILE(fp);
	return (pos);
}
